CdS photocatalyst for hydrogen production, preparation therefor and method for producing hydrogen by use of the same

Abstract

The present invention relates to a novel CdS photocatalyst for producing hydrogen from water by photoreaction and preparation therefor, and method for producing hydrogen by using of the CdS photocatalyst. The CdS photocatalyst is characterized by the following general formula V:wherein m represents a doped metal element as an electron acceptor, such as Pt, Ru, Ir, Co, Rh, Cu, Pd, Ni, or the oxidized compound of one of these metals; A represents a percentage by weight of m, ranging from 0.10 to 2.50; M is catalyst element, e.g. V, Cr, Al and P; and B represents a mole % of M(M+Cd), ranging from 0.05 to 20.00.

What is claimed is:  
     
       1. A CdS photocatalyst for the production of hydrogen, represented by the following formula V: 
       
         
           m(A)/Cd[M(B)]S  
         
       
       wherein m represents a doped metal element or an oxide thereof, the metal element being an electron acceptor selected from the group consisting of Pt, Ru, Ir, Co, Rh, Cu, Pd and Ni; 
       A represents a percentage by weight of m, ranging from 0.10 to 2.50;  
       M is a catalyst element selected from the group consisting of V, Cr, Al and P; and  
       B represents a mole % of M/(M+Cd), ranging from 0.05 to 20.00.  
     
     
       2. A CdS photocatalyst for the production of hydrogen in accordance with claim  1 , wherein the molar ratio of Cd:S is from 1:0.1 to 1:2.8. 
     
     
       3. A CdS photocatalyst for the production of hydrogen in accordance with claim  1 , wherein the molar ratio of Cd:S is from 1:0.6 to 1:1.4. 
     
     
       4. A method for preparing a CdS photocatalyst as claimed in claim  1 , comprising the steps of: dissolving a Cd-containing and M-containing compound in water; to the thus-obtained solution adding H 2 S or Na 2 S as a reactant, with stirring, to obtain a precipitant Cd[M]S; washing the precipitant with wash water until the pH of the wash water reaches 7; vacuum-drying the thus-washed precipitate in a nitrogen atmosphere at from 105 to 120° C. for about 1.5 to 3.0 hours; and doping the thus-dried Cd[M]S precipitate by adding a liquid m-containing compound thereto in an amount of about 0.10 to 2.50% by weight. 
     
     
       5. A method in accordance with claim  4 , in which the doping further includes UV illumination and sintering. 
     
     
       6. A method in accordance with claim  4 , wherein said M-containing compound comprises a member selected from the group consisting of VCl 3 , VOSO 4 , VOCl 3 , K 2 Cr 2 O 7 , Cr(NO 3 ) 3 , Al(NO 3 ) 3,  AlCl 3  and H 3 PO 2 . 
     
     
       7. A method in accordance with claim  4 , wherein said m-containing compound comprises a member selected from the group consisting of H 2 PtCl 6 , RuCl 3 , Co(NO 3 ) 2 , CoCl 2 , Co(CH 3 COO) 2 , RhCl 3 , Rh(NO 3 ) 3 IrCl 3 , Ni(NO 3 ) 2 , NiCl 2 , Pd(NO 3 ) 2 , CuCl 2 , Cu(NO 3 ) 2  and CuSO 4 . 
     
     
       8. A method in accordance with claim  4 , in which the doping includes UV illumination in a nitrogen atmosphere when m is platinum. 
     
     
       9. A method in accordance with claim  4 , in which the doping includes oxidation and reduction sintering after UV illumination when m is platinum. 
     
     
       10. A method in accordance with claim  9 , wherein the sintering is effected at a temperature of from 300 to 400° C. 
     
     
       11. A method in accordance with claim  4 , wherein the Cd-containing compound includes CdSO 4 .H 2 O or Cd(NO 3 ) 2 .4H 2 O. 
     
     
       12. A method in accordance with claim  4 , which comprises adding hydrochloric acid before drying when m is not platinum. 
     
     
       13. A method for producing hydrogen, which comprises irradiating, with visible light adjusted by a light filter or with sun light, an aqueous suspension of a photocatalyst of claim  1 , while stirring, which aqueous suspension comprises from 0.15 to 0.40 mols per liter of Na 2 S as an electron donor and from 0.2 to 0.5 mols per liter of NaH 2 PO 2  as a reducing agent. 
     
     
       14. A method in accordance with claim  13 , which comprises producing hydrogen at a temperature of from 10 to 60° C. in vacuum or at a pressure of up to 2 atmospheres.